Interactive input systems that allow users to inject input (i.e. digital ink, mouse events etc.) into an application program using an active pointer (eg. a pointer that emits light, sound or other signal), a passive pointer (eg. a finger, cylinder or other suitable object) or other suitable input device such as for example, a mouse or trackball, are known. These interactive input systems include but are not limited to: touch systems comprising touch panels employing analog resistive or machine vision technology to register pointer input such as those disclosed in U.S. Pat. Nos. 5,448,263; 6,141,000; 6,337,681; 6,747,636; 6,803,906; 7,232,986; 7,236,162; and 7,274,356 assigned to SMART Technologies ULC of Calgary, Alberta, Canada, assignee of the subject application, the contents of which are incorporated by reference; touch systems comprising touch panels employing electromagnetic, capacitive, acoustic or other technologies to register pointer input; tablet personal computers (PCs); laptop PCs; personal digital assistants (PDAs); and other similar devices.
U.S. Pat. No. 7,009,663 to Abileah et al. discloses a machine vision based interactive input system that includes an Active Matrix Liquid Crystal Display (AMLCD) display panel constructed so as to substitute certain of the display pixels throughout the display panel with a photo-sensitive thin film transistor (“photo TFT”). An array of the photo TFTs together with corresponding select and readout lines cooperate as an imaging system embedded into the LCD backplane. Inhibition of light transmission to certain of the photo TFTs in the array can be detected during voltage readout cycles thereby to detect whether and where the touch surface has been touched.
The embedded imaging system disclosed by Abileah et al. has wide applicability as a platform technology for interactive input systems. However, it will be understood that an interactive input system incorporating such an embedded imaging system will be of limited use for providing user input to application programs in a robust manner unless touch events can be reliably distinguished from other causes of changes in the light transmitted to the photo TFTs. For example, the quantity of ambient light may vary, as might the presence of non-pointer objects in the vicinity of the display panel. Furthermore, it would be useful for such an interactive input system to be capable of distinguishing touch events from hover events, so as to determine whether in fact a touch has occurred, and also to extend the pointer input region into three dimensions by including the touch surface and some of the space extending from it.
It is therefore an object of the present invention to provide a method and system for determining the location of a pointer in a pointer input region.